It is oftentimes desirable to align optical fibers with an electro-optic device, such as optical waveguides or other light sources. Such alignment is particularly desirable in order to maximize the percentage of light coupled from the light source or electro-optic device to the optical fiber and to thereby increase the transmission efficiency of the optical signals. However, the alignment of optical fibers is complicated by the relatively small sizes of both the optical fiber waveguide which, for example, can have a light transmitting core diameter of approximately 4 micrometers and the light source, such as an electro-optic device including an optical waveguide, which has approximately the same size.
Furthermore, it is often desirable to align not just one optical fiber, but numerous optical fibers with one or more light sources. For example, a plurality of optical fibers must commonly be aligned with respective ones of the plurality of optical waveguides of an electro-optic device. In these instances, the alignment of the optical fibers is typically further complicated by the relatively small lateral spacing between the optical fibers. Due to the relatively small lateral spacing between the optical fibers, the alignment of a first optical fiber can affect the positioning of adjacent optical fibers, thereby potentially misaligning the adjacent optical fibers.
In addition, the process of aligning optical fibers with respective optical waveguides is preferably readily repeatable to provide for mass production capabilities. However, the repeatability of conventional optical fiber alignment processes is diminished by the large number of optical fibers which must be intricately positioned for proper alignment. Notwithstanding these further difficulties in alignment, there is an increasing demand for methods and apparatus to align a plurality of closely spaced optical fibers, such as optical fibers having a lateral spacing of less than 500 micrometers, due to advances in technology which have led to significant reductions in the size of electro-optical devices,
Various methods have been proposed to align a single optical fiber with a variety of electro-optic devices. See, for example, U.S. Pat. No. 4,955,683 which was issued Sep. 11, 1992, to Nobuo Shiga, et al. and is assigned to Sumitomo Electric Industries, Ltd.; U.S. Pat. No. 4,798,439 which was issued Jan. 17, 1989, to Keith Preston and is assigned to British Telecommunications, PLC; U.S. Pat. No. 4,741,796 which was issued May 3, 1988, to Hans Althaus, et al. and is assigned to Siemens Aktiengesellschaft; U.S. Pat. No. 4,702,547 which was issued Oct. 27, 1987, to R. Scott Enochs and is assigned to Tektronix, Inc.; U.K. Patent Application GB 2,128,768 which was published May 2, 1984, and is assigned to Hitachi Ltd.; and U.K. Patent Application GB 2,146,841 which was published Apr. 24, 1985, and is assigned to Hitachi Ltd.
As illustrated by these patents and known to those skilled in the art, individual metallized optical fibers can be soldered to a support. In order to position the optical fiber, the solder bonding the metallized optical fiber to the support is generally heated to a temperature above the predetermined melting temperature of the solder. Thereafter, the optical fiber can be moved and, once the optical fiber is properly positioned, the solder can be allowed to cool and resolidify to fix the position of the optical fiber relative to the support and, more importantly, to a light source.
In particular, U.S. Pat. No. 4,798,439 to Keith Preston (hereinafter the "'439 patent") describes an optical assembly and a related method for mounting optical components, such as an optical fiber, on a substrate. According to the '439 patent, an optical fiber is lowered into a layer of solder, such as a solder preform or a solder paste, which has been applied to a submount assembly. Thereafter, a heating element is lowered into contact with the solder to locally melt the solder about the optical fiber such that the optical fiber can be mounted therein. During the mounting process, a first end of the optical fiber is positioned to receive the output of a laser, also illustratively mounted on the submount assembly. By positioning the optical fiber such that the power level of the light transmitted through the optical fiber is maximized, the optical fiber is appropriately aligned with the laser. Once aligned, the heating element is cooled to allow the solder to solidify and to fix the optical fiber to the submount assembly.
Another method of positioning an optical fiber is described in U.S. Pat. No. 4,741,796 to Hans Althaus, et al. (hereinafter the "'796 patent"). In particular, the '796 patent describes a method for aligning an optical fiber with a laser diode. According to this method, an electrically conductive body having a groove defined therein is bonded to a base. An optical fiber extends through the groove and is bonded to the electrically conductive body with a bonding agent. By inducing current flow through the electrically conductive body, the temperature of the electrically conductive body is increased such that the optical fiber is positionable within the bonding agent. After properly positioning the optical fiber relative to the laser diode, the current flow is stopped to cool and solidify the bonding agent, thereby fixing the position of the optical fiber. However, neither the '439 patent nor the '796 patent describes a method or apparatus for attaching a plurality of laterally spaced optical fibers to a fixture and for thereafter individually aligning the plurality of optical fibers.